JP7087464B2 - A method for manufacturing a ferrite sintered magnet, a method for manufacturing ferrite particles, and a method for manufacturing a bonded magnet. - Google Patents

Description

The present invention relates to a method for producing a ferrite sintered magnet, a method for producing ferrite particles, and a method for producing a bonded magnet.

As the magnetic material used for the ferrite sintered magnet, Ba ferrite, Sr ferrite and Ca ferrite having a hexagonal crystal structure are known. As such a ferrite crystal structure, a magnetoplumbite type (M type), a W type, and the like are known. Among these, M-type ferrite is mainly adopted as a magnet material for motors and the like. The M-type ferrite is usually represented by the general formula of AFe ₁₂ O ₁₉ .

As an index of the magnetic characteristics of the ferrite sintered magnet, the residual magnetic flux density (Br), the coercive force (HcJ), and the square ratio (Hk / HcJ) are generally used. Conventionally, from the viewpoint of improving Br and HcJ, it has been attempted to add various elements different from the constituent elements of ferrite to ferrite. For example, in Patent Document 1, it is attempted to improve the magnetic properties by substituting a part of the element of A site with Ca and a rare earth element (R) and a part of Fe with Co.

International Publication No. 2008/146712

Motors, generators, etc., which are the main applications of ferrite sintered magnets, are being miniaturized in each technical field. For this reason, the internal structure is becoming complicated, and the installation space for magnets is becoming smaller. Therefore, it is conceivable to reduce the thickness in order to reduce the installation space. However, if the thickness is reduced, there is a concern that the ferrite sintered magnet will be demagnetized by the demagnetizing field.

An object of the present invention is to provide a method for manufacturing a ferrite sintered magnet having a high coercive force, a method for manufacturing ferrite particles having a high coercive force, and a method for manufacturing a bonded magnet using the ferrite particles.

(Manufacturing method of ferrite sintered magnet)
The method for manufacturing a ferrite sintered magnet according to one aspect of the present invention is a method for manufacturing a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure, in which a mixture containing raw materials for the ferrite phase is calcined. Then, a calcining process for producing ferrite particles, a molding process for forming an intermediate material containing ferrite particles to produce a molded body, a mixture of boric acid before calcining, and a pre-molding process. It comprises an addition step of adding to at least one of the intermediate materials of the above, and a firing step of sintering the compact, and the hoe with respect to the total mass of the mixture containing boric acid or the total mass of the intermediate material containing boric acid. The proportion of acid is greater than 0.3% by mass and less than 2.5% by mass.

The raw material of the ferrite phase may be a compound of a rare earth element R, a compound of an alkaline earth metal element A, a compound of iron, and a compound of cobalt, and R is at least one element selected from the rare earth elements. Well, A may be a combination of at least one alkaline earth metal element other than calcium and calcium, or calcium alone, relative to the total mass of the mixture containing boric acid, or the total mass of the intermediate material containing boric acid. The proportion of the compound of the rare earth element R may be 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R, and the mass of the entire mixture containing boric acid or the intermediate containing boric acid. The ratio of the compound of the alkaline earth metal element A to the total mass of the material may be 1.7% by mass or more and 7.6% by mass or less in terms of the mass of the oxide of A, and the ratio of the entire mixture containing boric acid may be. The ratio of the iron compound to the mass or the mass of the entire intermediate material containing boric acid may be 45.3 mass% or more and 87.4 mass% or less in terms of the mass of the iron oxide, and contains boric acid. The ratio of the cobalt compound to the total mass of the mixture or the total mass of the intermediate material containing boric acid may be 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the oxide of cobalt, and ferrite. The metal component contained in the phase may be expressed as R _1-x A _x F my _Coy , x may satisfy 0.2 ≦ x ≦ 0.8, and y may satisfy 0.1 ≦ _y ≦. 0.65 may be satisfied, m may satisfy ₃ ≦ m <14, and the boron content in the ferrite sintered magnet is 0.1% by mass or _more and 0.6 mass in terms of mass of B2O3. It may be less than or equal to%.

In the addition step, boric acid and silicon dioxide may be added to the mixture or intermediate material, and the ratio of silicon dioxide to the total mass of the mixture containing boric acid and silicon dioxide is greater than 0% by mass and 5% by mass or less. Alternatively, the ratio of silicon dioxide to the total mass of the intermediate material containing boric acid and silicon dioxide may be greater than 0% by mass and 5% by mass or less.

The ratio of boric acid to the mass of the whole mixture or the whole intermediate material may be 0.6% by mass or more and 1.5% by mass or less.

The ratio of boric acid to the mass of the whole mixture or the whole intermediate material may be 0.7% by mass or more and 1.2% by mass or less.

The ratio of silicon dioxide to the total mass of the mixture containing boric acid and silicon dioxide may be greater than 0% by weight and less than 0.2% by mass, or to the total mass of intermediate material containing boric acid and silicon dioxide. The proportion of silicon dioxide may be greater than 0% by weight and less than 0.2% by weight.

At least one of the mixture before calcination and the intermediate material before molding may contain water.

(Manufacturing method of ferrite particles)
The method for producing ferrite particles according to one aspect of the present invention is a method for producing ferrite particles containing a ferrite phase having a magnetoplumbite-type crystal structure, in which a mixture containing a raw material for the ferrite phase and boric acid is heated. In addition, a heating step for producing ferrite particles is provided, and the ratio of boric acid to the total mass of the mixture containing boric acid is larger than 0.3% by mass and 2.5% by mass or less.

The raw material of the ferrite phase may be a compound of a rare earth element R, a compound of an alkaline earth metal element A, a compound of iron, and a compound of cobalt, and R is at least one element selected from the rare earth elements. Often, A may be a combination of at least one alkaline earth metal element other than calcium and calcium, or calcium alone, and the ratio of the compound of the rare earth element R to the total mass of the mixture containing boric acid is R. In terms of the mass of the oxide, it may be 5.5% by mass or more and 19.9% by mass or less, and the ratio of the compound of the alkaline earth metal element A to the total mass of the mixture containing boric acid is that of the oxide of A. In terms of mass, it may be 1.7% by mass or more and 7.6% by mass or less, and the ratio of the iron compound to the total mass of the mixture containing boric acid is 45.3 mass in terms of the mass of the iron oxide. % Or more and 87.4% by mass or less, and the ratio of the element of the cobalt to the total mass of the mixture containing boric acid is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the oxide of cobalt. The metal component contained in the ferrite phase may be expressed as R _1-x A _x F my _Coy , x may satisfy 0.2 ≦ x ≦ 0.8, and _y may be satisfied. 0.1 ≦ y ≦ 0.65 may be satisfied, m may satisfy 3 ≦ m <14, and the boron content in the ferrite particles is 0.1% by mass or more in terms of mass of B ₂ O ₃ . It may be 0.6% by mass or less.

Boric acid and silicon dioxide may be added to the mixture, and the ratio of silicon dioxide to the total mass of the mixture containing boric acid and silicon dioxide may be greater than 0% by mass and 5% by mass or less.

The ratio of boric acid to the total mass of the mixture may be 0.6% by mass or more and 1.5% by mass or less.

The ratio of boric acid to the total mass of the mixture may be 0.7% by mass or more and 1.2% by mass or less.

The ratio of silicon dioxide to the total mass of the mixture containing boric acid and silicon dioxide may be greater than 0% by mass and less than 0.2% by mass.

The mixture before heating may contain water.

(Manufacturing method of bond magnet)
The method for manufacturing a bonded magnet according to one aspect of the present invention includes a step of manufacturing a molded body containing ferrite particles and a resin, and a step of curing the resin in the molded body, and the ferrite particles are produced as described above. Manufactured by the method.

According to the present invention, it is possible to provide a method for manufacturing a ferrite sintered magnet having a high coercive force, a method for manufacturing ferrite particles having a high coercive force, and a method for manufacturing a bonded magnet using the ferrite particles.

Some embodiments of the present invention will be described in detail below. The present invention is not limited to the following embodiments.

(Manufacturing method of ferrite particles and manufacturing method of ferrite sintered magnet)
The method for manufacturing a ferrite sintered magnet according to the present embodiment is a method for manufacturing a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure. The method for producing ferrite particles according to the present embodiment is a method for producing ferrite particles containing a ferrite phase having a magnetoplumbite-type crystal structure. As will be described later, the method for producing ferrite particles may be a part of the method for producing a ferrite sintered magnet.

The method for manufacturing a ferrite sintered magnet includes at least an addition step, a calcining step, a molding step, and a firing step. In the calcination step, a mixture containing a ferrite phase raw material is calcified to produce ferrite particles (temporary baking powder). In the molding step, an intermediate material containing ferrite particles is molded to produce a molded product. In the firing step, the compact is sintered.

In the addition step, boric acid (H ₃ BO ₃ ) is added to at least one of the mixture before calcination and the intermediate material before molding. That is, the addition step may be carried out before the calcining step. The addition step may be carried out after the calcining step (before the molding step). The addition step may be carried out before and after the calcining step. The ratio of boric acid to the total mass of the mixture containing boric acid or the total mass of the intermediate material containing boric acid is more than 0.3% by mass and 2.5% by mass or less. At least one of the mixture before calcination and the intermediate material before molding may contain water. In the addition step, the aqueous solution of boric acid may be added to at least one of the mixture before calcination and the intermediate material before molding. When the proportion of boric acid in the mixture before calcination is adjusted to a range of more than 0.3% by mass and 2.5% by mass or less, boric acid is added to the intermediate material before molding. It does not have to be added. If the proportion of boric acid in the mixture before calcination is greater than 0.3% by weight and less than 2.5% by weight, the proportion of boric acid in the intermediate material before molding is 0. It may be adjusted within the range of more than 3% by mass and not more than 2.5% by mass. For example, when the ratio of boric acid added to the mixture before the calcining step is 0.3% by mass or less with respect to the whole mixture, boric acid is further added to the intermediate material before molding. Therefore, the proportion of boric acid in the intermediate material may be adjusted within the range of more than 0.3% by mass and 2.5% by mass or less. When the ratio of boric acid added to the mixture before the calcining step exceeds 2.5% by mass with respect to the whole mixture, the raw material of the ferrite phase or the raw material of the auxiliary component with respect to the intermediate material before molding ( By further adding a sintering aid or the like), the proportion of boric acid in the intermediate material may be adjusted within the range of more than 0.3% by mass and 2.5% by mass or less.

The method for producing ferrite particles includes at least a heating step. In the heating step, a mixture containing a ferrite phase raw material and boron is heated to prepare ferrite particles. The ratio of boric acid to the total mass of the mixture containing boric acid is greater than 0.3% by mass and less than 2.5% by mass. The mixture before heating may contain water.

When the addition step is performed before the calcining step in the method for manufacturing a ferrite sintered magnet, the calcining step in the method for manufacturing a ferrite sintered magnet is equivalent to the heating step in the method for manufacturing ferrite particles. That is, when the addition step is carried out before the calcining step in the method for manufacturing a ferrite sintered magnet, each step up to the calcining step in the method for manufacturing a ferrite sintered magnet is substantially the same as the method for manufacturing ferrite particles. It is the same.

By adding boric acid to the mixture containing the raw material of the ferrite phase, ferrite particles and ferrite sintered magnets having high coercive force can be obtained. Further, by adding boric acid to an intermediate material containing ferrite particles, a ferrite sintered magnet having a high coercive force can be obtained. In the following, a mixture containing a raw material for a ferrite phase is referred to as a "raw material mixture". The reason why the addition of boric acid to the raw material mixture improves the magnetic properties (particularly the coercive force) of the ferrite particles and the ferrite sintered magnet is as follows, but is not necessarily limited to the following.

The solubility of boric acid in water is higher than the solubility of boron oxide (B ₂ O ₃ ) in water. For example, the solubility of boric acid in water at 25 ° C. is about 5.7 g / 100 ml, and the solubility of boron oxide in water at 25 ° C. is about 3.6 g / 100 ml. Therefore, by mixing boric acid with water with the raw material mixture, boric acid can be more uniformly dispersed in the raw material mixture than boron oxide at the molecular level. Similarly, in intermediate materials containing boric acid, water, and ferrite particles, boric acid can be more uniformly dispersed at the molecular level than boron oxide. Further, since the specific gravity of boric acid (1.5 g / cm ³ ) is smaller than the specific gravity of boron oxide (1.9 g / cm ³ or more), boric acid is more easily dispersed by stirring and mixing than that of boron oxide. Furthermore, boric acid decomposes even at a relatively low temperature as compared with boron oxide. For example, boric acid decomposes at 171 ° C, while boron oxide decomposes at 450 ° C. Therefore, even if undissolved boric acid remains in the raw material mixture, boric acid is easily decomposed in the calcination step, and boron is easily dispersed uniformly in the ferrite particles. For the same reason, even if undissolved boric acid remains in the intermediate material, boric acid is easily decomposed in the firing step and boron is easily dispersed uniformly in the ferrite sintered magnet.

Since there is a difference between boric acid and boron oxide as described above, in the present embodiment using boric acid, variation in the particle size of the ferrite particles is suppressed. Then, by sintering the ferrite particles having a substantially uniform particle size, a uniform fine structure is formed in the ferrite sintered magnet.

Further, as described above, the ratio of boric acid to the total mass of the mixture containing boric acid or the total mass of the intermediate material containing boric acid is larger than 0.3% by mass and 2.5% by mass or less. As a result, the content of boron in the ferrite particles or the ferrite sintered magnet is easily adjusted to 0.1% by mass or _more and 0.6% by mass or less in terms of mass of _B2O3 .

For the above reasons, it becomes possible to obtain ferrite particles and ferrite sintered magnets having excellent magnetic properties (particularly high coercive force).

Since the coercive force of ferrite particles and ferrite sintered magnets tends to increase, the ratio of boric acid to the mass of the entire raw material mixture or intermediate material is 0.6% by mass or more and 1.5% by mass or less, or 0.7% by mass. It may be% or more and 1.2% by mass or less.

In the addition step, boric acid and silicon dioxide (SiO ₂ ) may be added to the mixture or intermediate material. The ratio of silicon dioxide to the total mass of the mixture containing boric acid and silicon dioxide may be greater than 0% by mass and 5% by mass or less, or greater than 0% by mass and less than 0.2% by mass. Alternatively, the ratio of silicon dioxide to the total mass of the intermediate material containing boric acid and silicon dioxide may be greater than 0% by mass and 5% by mass or less, or greater than 0% by mass and less than 0.2% by mass. By adding silicon dioxide to the mixture, the raw material of the ferrite phase can be easily sintered in the calcining step, and ferrite particles having a high coercive force can be easily obtained. That is, silicon dioxide functions as a sintering aid. By adding silicon dioxide to the intermediate material, the ferrite particles in the molded body can be easily sintered with each other in the firing step, and a ferrite sintered magnet having a high coercive force can be easily obtained.

If the proportion of silicon dioxide in the pre-baked mixture is adjusted to within the above range, silicon dioxide may not be added to the pre-molded intermediate material. If the proportion of silicon dioxide in the mixture before calcination is outside the above range, the proportion of silicon dioxide in the intermediate material before molding may be adjusted within the above range. For example, if the proportion of silicon dioxide added to the mixture before the calcination step is too small, the proportion of silicon dioxide in the intermediate material can be increased by adding more silicon dioxide to the intermediate material before molding. It may be adjusted within the range. If the proportion of silicon dioxide added to the mixture before the calcination step is too large, the intermediate material may be added by further adding the raw material of the ferrite phase, the raw material of the auxiliary component, boric acid, etc. to the intermediate material before molding. The proportion of silicon dioxide in the material may be adjusted within the above range.

The details of each process are as follows.

The method for producing a ferrite sintered magnet may include a compounding step, a calcining step (heating step), a crushing step, a molding step, and a firing step. As described above, when the addition step is carried out before the calcining step in the method for manufacturing a ferrite sintered magnet, the compounding step and the calcining step in the method for manufacturing a ferrite sintered magnet correspond to the method for manufacturing ferrite particles. ..

In the compounding step, a plurality of raw materials for forming a ferrite phase are compounded to obtain a raw material mixture. In the compounding step, boric acid may be added to the raw material mixture. That is, the compounding step may also serve as an addition step.

The raw material of the ferrite phase may be a compound of a rare earth element R, a compound of an alkaline earth metal element A, a compound of iron (Fe), and a compound of cobalt (Co). R may be at least one element selected from rare earth elements. That is, R is scandium (Sc), yttrium (Y), lantern (La), cerium (Ce), placeodim (Pr), neodym (Nd), samarium (Sm), europium (Eu), gadrinium (Gd), terbium. It may be at least one selected from the group consisting of (Tb), dysprosium (Dy), formium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). A may be a combination of at least one alkaline earth metal element other than calcium and calcium. The alkaline earth metal element other than calcium may be at least one of Sr and Ba. A may be calcium only. The raw material compound may be, for example, an oxide of each of R, A, Fe and Co, or a compound (carbonate, hydroxide, nitrate, etc.) that becomes these oxides by firing. Specific examples of the raw material compound include SrCO ₃ , La (OH) ₃ , Fe ₂ O ₃ , BaCO ₃ , CaCO ₃ and Co ₃ O ₄ . The raw material compound is preferably, for example, a powder. The average particle size of the powder of the raw material compound may be, for example, about 0.1 to 2.0 μm from the viewpoint of facilitating the blending of the raw material compound.

The metal component contained in the ferrite phase (magnetoplambite-type ferrite) formed from the above raw materials may be represented by the following general formula (I). The atomic ratio x (molar ratio) in the general formula (I) may satisfy the following formula (1). The atomic ratio y (molar ratio) in the general formula (I) may satisfy the following formula (2). The atomic ratio m (molar ratio) in the general formula (I) may satisfy the following formula (3).
R _{1-x A x} F my _Coy (I)
0.2 ≤ x ≤ 0.8 (1)
0.1 ≤ y ≤ 0.65 (2)
3 ≤ m <14 (3)

The ferrite phase (magnetoplumbite-type ferrite) is an oxide of R _{1-x A x} F my _Coy . For example, the magnetoplumbite type ferrite may be represented by the following formula (Ia). The x, y and m of the following formula (Ia) are the same as the x, y and m of the above formula (I). As long as the hexagonal structure of the magnetoplumbite-type ferrite is established, the atomic ratio z (molar ratio) of O in the following formula (Ia) is not limited. z may satisfy, for example, 11 <z <27. z may be 19. In a part of the ferrite particles or the ferrite sintered magnet, z may vary in the vicinity of 19.
R _{1-x A x} Fe my _{Coy Oz} (Ia)

The ratio of the rare earth element R compound to the total mass of the raw material mixture containing boric acid or the total mass of the intermediate material containing boric acid is 5.5% by mass or more and 19.9% by mass in terms of the mass of the oxide of R. It may be as follows. When the ratio of the compound of R is 5.5% by mass or more and 19.9% by mass or less, the atomic ratio (1-x) of R in the above general formulas (I) and (Ia) is 0.2 ≦. It is easy to adjust to the range of 1-x ≦ 0.8.

The ratio of the compound of the alkaline earth metal element A to the total mass of the raw material mixture containing boric acid or the total mass of the intermediate material containing boric acid is 1.7% by mass or more in terms of the mass of the oxide of A. It may be 6% by mass or less. Since the ratio of the compound of A is 1.7% by mass or more and 7.6% by mass or less, the atomic ratio x of A in the above general formulas (I) and (Ia) is 0.2 ≦ x ≦ 0. It is easy to adjust to the range of 8, and the atomic ratio (1-x) of R is easy to adjust to the range of 0.2 ≦ 1-x ≦ 0.8.

The ratio of the iron compound to the total mass of the raw material mixture containing boric acid or the total mass of the intermediate material containing boric acid is 45.3% by mass or more and 87.4% by mass or less in terms of the mass of iron oxide. It may be there. Since the ratio of iron oxide is 45.3% by mass or more and 87.4% by mass or less, the atomic ratio (my) of Fe in the above general formulas (I) and (Ia) is 2. It is easy to adjust to the range of 35 ≦ my <13.9.

The ratio of the cobalt compound to the total mass of the raw material mixture containing boric acid or the total mass of the intermediate material containing boric acid is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the cobalt oxide. It may be there. Since the ratio of the cobalt oxide is 0.9% by mass or more and 18.9% by mass or less, the atomic ratio y of Co in the general formulas (I) and (Ia) is 0.1 ≦ y ≦ 0. It is easy to adjust to the range of 65, and the atomic ratio (my) of Fe is easy to adjust to the range of 2.35 ≦ my <13.9.

In the compounding step, each raw material and boric acid may be mixed so that the compounding ratio (mass ratio) of each raw material of the ferrite phase matches the composition represented by the general formulas (I) and (Ia). Each mixed raw material and boric acid are mixed and pulverized for about 0.1 to 20 hours using a wet attritor, a ball mill or the like to obtain a raw material mixture. In the blending step, if necessary, a raw material compound (elemental substance or oxide, etc.) as an auxiliary component may be blended into the raw material mixture. By mixing and pulverizing each raw material, water and boric acid by a wet method, it is easy to obtain a raw material mixture in which boric acid is uniformly dispersed.

In the calcining step (heating step), the raw material mixture obtained in the blending step is calcined. By the calcination step, granular or lumpy calcination powder (coarse ferrite particles) is obtained. The calcining is preferably performed in an oxidizing atmosphere such as air. The temperature of the calcination may be 1100 to 1400 ° C, 1100 to 1300 ° C, or 1100 to 1250 ° C. The calcination time may be 1 second to 10 hours, or 1 second to 3 hours. The ratio of the ferrite phase (M phase) in the calcined powder (ferrite particles) obtained by calcining may be, for example, 70% by volume or more, or 75% by volume or more. The ratio of the ferrite phase is obtained by the same method as the ratio of the ferrite phase in the ferrite sintered magnet.

In the crushing step, the calcined powder is crushed. The pulverization step may include, for example, a coarse pulverization step of coarsely pulverizing the calcination powder, and a fine pulverization step of further pulverizing the calcination powder following the coarse pulverization step. That is, the crushing step may be performed in two steps.

In the coarse pulverization step, for example, a vibration mill or the like may be used. The average particle size of the powder (coarse pulverized material) obtained by coarse pulverization of the calcination powder may be 0.5 to 5.0 μm. In the fine pulverization step, the coarse pulverized material is further pulverized by a wet attritor, a ball mill, a jet mill or the like. The average particle size of the pulverized material obtained by pulverization may be about 0.08 to 2.0 μm, 0.1 to 1.0 μm, or 0.2 to 0.8 μm. The specific surface area (BET specific surface area) of the finely pulverized material may be about 7 to 12 m ² / g. The suitable grinding time depends on the grinding method. For example, in the case of a wet attritor, the pulverization time may be 30 minutes to 10 hours. The time of wet pulverization by a ball mill may be about 10 to 50 hours.

By carrying out the pulverization step by a wet method, calcined powder (ferrite particles), water and boric acid are mixed and pulverized, and it is easy to obtain an intermediate material in which boric acid is uniformly dispersed.

When boric acid is added to the raw material mixture before calcination, the above steps complete the ferrite particles. When forming a ferrite sintered magnet from ferrite particles, the following steps are further carried out.

When forming a ferrite sintered magnet from ferrite particles, boric acid may be added to the calcined powder prior to the pulverization step. That is, the above addition step may be carried out at a time point between the calcining step and the crushing step. Prior to the grinding step, not only boric acid but also silicon dioxide may be added to the calcined powder. Boric acid may be added to the calcined powder at the time point between the coarse grinding step and the fine grinding step. That is, the above addition step may be carried out at a time point between the coarse pulverization step and the fine pulverization step. At the time point between the coarse grinding step and the fine grinding step, not only boric acid but also silicon dioxide may be added to the calcined powder.

In the fine pulverization step, in order to increase the degree of magnetic orientation of the sintered body (ferrite sintered magnet) obtained in the firing step, for example, the polyhydric alcohol represented by the general formula C _n (OH) _n H _{n + 2} is transferred to the coarse pulverized material. May be added. N in the general formula for polyhydric alcohols may be 4 to 100, 4 to 30, 4 to 20 or 4 to 12. Examples of the polyhydric alcohol include sorbitol. Further, two or more kinds of polyhydric alcohols may be used in combination. Further, in addition to the polyhydric alcohol, other dispersants may be used in combination.

The amount of the polyhydric alcohol added is 0.05 to 5.0% by mass, 0.1 to 3.0% by mass, or 0.2 to 2.0% by mass with respect to the object to be added (for example, ferrite particles). May be%. The polyhydric alcohol added in the fine pulverization step is removed by thermal decomposition in the firing step described later.

By the above steps, an intermediate material containing at least ferrite particles can be obtained. The intermediate material may contain, in addition to the ferrite particles, at least one selected from the group consisting of boric acid, a sintering aid (silicon dioxide or calcium carbonate, etc.), water, a polyhydric alcohol, and a dispersant. The intermediate material may be a slurry containing water.

In the molding step, an intermediate material containing ferrite particles is molded in a magnetic field to obtain a molded product. Molding can be performed by either drywall molding or wet molding. Wet molding is preferable from the viewpoint of increasing the degree of magnetic orientation.

In the case of wet molding, for example, by performing the above-mentioned fine pulverization step in a wet manner, a slurry of an intermediate material containing ferrite particles is obtained, and then this slurry is concentrated to obtain a slurry for wet molding. This wet molding slurry is molded. The slurry can be concentrated by centrifugation, filter press, or the like. The content of ferrite particles (finely pulverized material) in the wet forming slurry may be 30 to 80% by mass. In the slurry, water is preferable as the dispersion medium for dispersing the ferrite particles. In this case, a surfactant such as gluconic acid, gluconate, and sorbitol may be added to the slurry. Moreover, you may use a non-aqueous solvent as a dispersion medium. As the non-aqueous solvent, an organic solvent such as toluene or xylene can be used. In this case, it is preferable to add a surfactant such as oleic acid to the non-aqueous solvent. A wet molding slurry may be prepared by adding a dispersion medium or the like to the dried ferrite particles.

When the wet molding slurry is molded in a magnetic field, the molding pressure may be about 9.8 to 49 MPa (0.1 to 0.5 ton / cm ² ), and the applied magnetic field is 398 to 1194 kA / m (5). It may be about ~ 15 kOe).

In the firing step, the molded body obtained in the molding step is sintered to obtain a sintered body (ferrite sintered magnet). That is, a ferrite sintered magnet is formed by sintering the innumerable ferrite particles (fine pulverized materials) constituting the molded body to each other.

Firing can be performed in an oxidizing atmosphere such as the atmosphere. The firing temperature may be 1050 to 1270 ° C, or 1080 to 1240 ° C. The firing time (time for maintaining the firing temperature) may be about 0.5 to 3 hours.

When the molded product produced by wet molding is fired without being sufficiently dried, the dispersion medium or the like in the molded product may violently volatilize due to rapid heating, and cracks may occur in the molded product. From the viewpoint of suppressing cracks, before heating the molded body at the above firing temperature, the molded body is sufficiently dried by heating, for example, from room temperature to about 100 ° C. at a heating rate of about 0.5 ° C./min. It's okay. When the molded product contains a surfactant (dispersant) or the like, for example, the molded product is heated at a heating rate of about 2.5 ° C./min in a temperature range of about 100 to 500 ° C. to obtain a surfactant (a surfactant). Dispersant) and the like may be removed (defatting treatment). These heat treatments may be carried out at the beginning of the firing step, or may be carried out as a separate step prior to the firing step.

By the above steps, the ferrite sintered magnet is completed.

The above-mentioned molding step and firing step may be performed by the following procedure.

The molding step may be performed by a CIM (Ceramic Injection Molding) molding method or a PIM (Power Injection Molding, a type of powder injection molding). In the CIM molding method, first, a dried intermediate material (a type of powder injection molding) may be used. Ferrite particles) are heat-kneaded together with a binder resin to form pellets. The pellets are injection-molded in a mold to which a magnetic field is applied to obtain a preformed body. By debindering the preformed body. A molded product is obtained. A more detailed procedure will be described below.

The slurry of the intermediate material (slurry containing ferrite particles) obtained by wet grinding is dried. The drying temperature is preferably 80 to 150 ° C, more preferably 100 to 120 ° C. The drying time is preferably 1 to 40 hours, more preferably 5 to 25 hours. The average particle size of the primary particles of the intermediate material (ferrite particles) after drying is preferably 0.08 to 2 μm, more preferably 0.1 to 1 μm.

The dried intermediate material is kneaded with organic components such as binder resin, waxes, lubricants, plasticizers, and sublimable compounds, and molded into pellets with a pelletizer or the like. The proportion of the organic component in the molded product is preferably 35 to 60% by volume, more preferably 40 to 55% by volume. The kneading may be performed by, for example, a kneader. As the pelletizer, for example, a twin-screw single-screw extruder is used. Kneading and pellet molding may be carried out while heating depending on the melting temperature of the organic component used.

As the binder resin, a polymer compound such as a thermoplastic resin is used. Examples of the thermoplastic resin include polyethylene, polypropylene, ethylene vinyl acetate copolymer, atactic polypropylene, acrylic polymer, polystyrene, polyacetal and the like.

As the waxes, in addition to natural waxes such as carnauba wax, montan wax and beeswax, synthetic waxes such as paraffin wax, urethanized wax and polyethylene glycol are used.

Examples of the lubricant include fatty acid esters and the like. Examples of the plasticizer include phthalates.

The amount of the binder resin added is preferably 3 to 20% by mass with respect to 100% by mass of the ferrite particles. The amount of wax added is preferably 3 to 20% by mass with respect to 100% by mass of the ferrite particles. The amount of the lubricant added is preferably 0.1 to 5% by mass with respect to 100% by mass of the ferrite particles. The amount of the plasticizer added is preferably 0.1 to 5% by mass with respect to 100% by mass of the binder resin.

Next, the pellets are injected into the mold using a magnetic field injection molding device to form the pellets. Before the pellet is injected into the mold, the mold is closed and a magnetic field is applied to the mold with a cavity formed inside the mold. Inside the extruder, the pellets are heated and melted to 160-230 ° C. and ejected into the mold cavity by a screw. The temperature of the mold may be 20 to 80 ° C. The magnetic field applied to the mold may be 398 to 1592 kA / m (5 to 20 kOe). By such injection molding, a preformed body is obtained.

The obtained preformed body is heat-treated at a temperature of 100 to 600 ° C. in the air or nitrogen to perform a binder removal treatment to obtain a molded product. When a plurality of kinds of organic components are used, the binder removal treatment may be carried out in a plurality of times.

In the firing step, the molded body that has undergone the binder removal treatment is sintered in the air to obtain a ferrite sintered magnet. The firing temperature may be preferably 1100 to 1250 ° C, more preferably 1160 to 1230 ° C, and the firing time may be about 0.2 to 3 hours.

(Manufacturing method of bond magnet)
The method for manufacturing a bonded magnet in the present embodiment includes a step of manufacturing a molded body containing the ferrite particles and the resin manufactured by the above method, and a step of curing the resin in the molded body to obtain a bonded magnet. To prepare for. For example, a bonded magnet can be obtained by impregnating a molded product produced by the above molding step with a thermosetting resin and curing the thermosetting resin in the molded product by heating. The details of the manufacturing method of the bonded magnet are as follows.

The molded product is immersed in the resin-containing solution in the container. Seal the container containing the molded product and the resin-containing solution. The reduced pressure in the closed container defoams the molded body and allows the resin-containing solution to permeate into the voids in the molded body. The defoamed molded product is taken out from the resin-containing solution, and the excess resin-containing solution adhering to the surface of the molded product is removed. A centrifuge or the like may be used to remove the excess resin-containing solution.

Before immersing the molded body in the resin-containing solution, the molded body and the solvent (toluene, etc.) are placed in a closed container, and the molded body is immersed in the solvent while reducing the pressure inside the container to defoam the molded body. Is promoted. As a result, the resin easily penetrates into the molded body, and the voids in the molded body are easily reduced.

The method for manufacturing a bonded magnet is not limited to the above example. For example, a compound may be prepared by mixing ferrite particles and a resin, and the compound may be molded in a magnetic field to prepare a molded product containing the ferrite particles and the resin.

(Ferrite sintered magnet and ferrite particles)
The ferrite sintered magnet and the ferrite particles have a ferrite phase (main phase) having a magnetoplobite type crystal structure. The main phase refers to the crystal phase most contained in ferrite sintered magnets and ferrite particles. The ferrite sintered magnet and the ferrite particles may have a crystal phase (different phase) different from that of the main phase.

The metal component contained in the ferrite phase is represented by the following general formula (I) and satisfies the following formulas (1), (2) and (3). In the general formula (I), x, y and m are atomic ratios (molar ratios). As described above, R in the general formula (I) is at least one element selected from rare earth elements. A may be a combination of Ca and at least one selected from Sr and Ba. A may be Ca only.
R _{1-x A x} F my _Coy (I)
0.2 ≤ x ≤ 0.8 (1)
0.1 ≤ y ≤ 0.65 (2)
3 ≤ m <14 (3)

X in the general formula (I) may be 0.7 or less, or may be 0.6 or less, from the viewpoint of further increasing the coercive force. From the same viewpoint, x may be 0.25 or more, or may be 0.3 or more. Y in the general formula (I) may be 0.6 or less or 0.5 or less from the viewpoint of further enhancing the magnetic characteristics. From the same viewpoint, y in the general formula (I) may be 0.15 or more, or may be 0.2 or more. M in the general formula (I) may be 4 or more or 5 or more from the viewpoint of further increasing the coercive force. From the same viewpoint, m in the general formula (I) may be 13 or less, or may be 12 or less.

From the viewpoint of enhancing the magnetic properties, it is preferable that A in the general formula (I) contains Ca and Sr as main components. A may consist only of Ca and Sr. From the viewpoint of increasing the magnetic properties, A may be Ca alone.

The metal component contained in the ferrite phase may be represented by the following general formula (II), and may satisfy the following formulas (4), (5), (6) and (7). That is, x1, x2, y and m in the general formula (II) indicate the atomic ratio (molar ratio). X in the formula (I) is equal to x1 + x2 in the general formula (II). R in the general formula (II) is at least one element selected from rare earth elements. E in the general formula (II) represents at least one element selected from the group consisting of Sr and Ba.
R _{1-x1-x2 Ca x1} E _x2 Fe my _Coy (II)
0.1 ≤ x 1 ≤ 0.65 (4)
0≤x2 <0.5 (5)
0.1 ≤ y ≤ 0.65 (6)
3 ≤ m <14 (7)

X1 in the general formula (II) may be 0.7 or less, or may be 0.6 or less, from the viewpoint of further increasing the coercive force. From the same viewpoint, x1 may be 0.20 or more, or may be 0.3 or more. X2 in the general formula (II) may be 0.4 or less or 0.3 or less from the viewpoint of further increasing the coercive force. X2 in the general formula (II) may be 0.

Y in the general formula (II) may be 0.6 or less or 0.5 or less from the viewpoint of further enhancing the magnetic characteristics. From the same viewpoint, y in the general formula (II) may be 0.15 or more, or may be 0.2 or more. The m in the general formula (II) may be 4 or more or 5 or more from the viewpoint of further increasing the coercive force. From the same viewpoint, m in the general formula (II) may be 13 or less, or may be 12 or less.

The content ratio of each element represented by the general formula (I) and the general formula (II) can be measured by fluorescent X-ray analysis. The content ratio of each element represented by the general formula (I) and the general formula (II) may be the same as the ratio of each element in the above-mentioned raw material mixture. The boron content can be measured by inductively coupled plasma emission spectroscopy (ICP emission spectroscopy).

The content of _B in the ferrite sintered magnet and the ferrite particles may be 0.1 to 0.6% by mass in terms of _B2O3 . From the viewpoint of further enhancing the magnetic properties, the content of B may be 0.5% by mass or less, or 0.4% by mass or less. From the same viewpoint, the content of B may be 0.1% by mass or more, 0.14% by mass or more, or more than 0.2% by mass.

E in the general formula (II) preferably contains Sr as a main component from the viewpoint of enhancing the magnetic properties. E may consist only of Sr.

R in the general formula (I) and the general (II) preferably contains one or more elements selected from the group consisting of La, Ce, Pr, Nd and Sm. It is more preferable that R contains La. R may consist only of La.

The ferrite sintered magnet and the ferrite particles may contain an element not represented by the above general formula (I) or (II) as a sub-component. Examples of the sub-ingredients include Si and Na. These subcomponents may be contained in the ferrite sintered magnet and the ferrite particles as, for example, the respective oxides or composite oxides.

The content of Si in the ferrite sintered magnet and the ferrite particles may be, for example, 0 to 3% by mass in terms of the mass of SiO ₂ .

The Na content in ferrite sintered magnets and ferrite particles is, for example, 0 to 0.2% by mass, 0.01 to 0.15% by mass, or 0.02 to 0.1% by mass in terms of mass of Na _2O . May be%.

Ferrite sintered magnets and ferrite particles may contain unavoidable impurities in addition to the above-mentioned components. Examples of this unavoidable impurity include Ti (titanium), Cr (chromium), Mn (manganese), Mo (molybdenum), V (vanadium), Al (aluminum) and the like. These components may be contained in the ferrite sintered magnet and the ferrite particles as the respective oxides or composite oxides. The contents of the above-mentioned sub-components, impurities and unavoidable components can be measured by fluorescent X-ray analysis or ICP emission spectroscopic analysis. The sub-component may be segregated at the grain boundaries of the ferrite crystal grains in the ferrite sintered magnet to form a heterogeneous phase.

The average particle size of ferrite particles (crystal grains containing a ferrite phase) in a ferrite sintered magnet may be, for example, 5 μm or less, 4.0 μm or less, or 0.5 to 3.0 μm. May be good. When the ferrite particles have the above average particle size, the coercive force can be further increased. The average particle size of the crystal grains in the ferrite sintered magnet may be measured by observing the cross section of the ferrite sintered magnet with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). Image processing of an image of a cross section containing hundreds of crystal grains measures a particle size distribution based on the number of crystal grains contained in the cross section. From this particle size distribution, the average particle size based on the number of crystal grains is calculated. The average particle size of the powdery ferrite particles may be measured, for example, by a particle size distribution meter.

The coercive force of the ferrite sintered magnet and the ferrite particles is, for example, preferably 4900 Oe or more, and more preferably 5000 Oe or more. The residual magnetic flux density of the ferrite sintered magnet is preferably 3000 G or more, more preferably 3500 G or more.

The shape of the ferrite sintered magnet is not limited. For example, the shape of the ferrite sintered magnet may be one selected from the group consisting of an arc segment type, a C-shape, a tile shape, a flat plate, a polygonal column, a cylinder, and an arch shape.

(Bond magnet)
The bonded magnet contains a cured resin and a plurality of the above-mentioned ferrite particles bonded to each other via the resin. The resin may be a thermosetting resin such as an epoxy resin, a phenol resin, a resin having a polyaromatic ring, or a resin having a triazine ring (triazine resin). The resin may include a polyamide-based elastomer such as styrene-based, olefin-based, urethane-based, polyester-based, and nylon, and a thermoplastic resin such as ionomer, ethylene propylene copolymer (EPM), and ethylene-ethyl acrylate copolymer. ..

The resin content in the bonded magnet may be, for example, 0.5 to 10% by mass from the viewpoint of achieving both excellent magnetic properties and excellent mechanical strength (stability of the shape of the magnet). It may be up to 5% by mass. From the same viewpoint, the content of ferrite particles in the bonded magnet may be, for example, 90 to 99.5% by mass or 95 to 99% by mass. The resin content in the bond magnet is adjusted by the concentration of the resin in the resin-containing solution used for production, the molding pressure in the molding process, and the like.

The shape of the bond magnet is not limited. For example, the shape of the bond magnet may be one selected from the group consisting of an arc segment shape, a C shape, a tile shape, a flat plate, a polygonal prism, a cylinder, and an arch shape.

(Use of ferrite sintered magnets and bonded magnets)
The ferrite sintered magnet and the bonded magnet according to this embodiment have a high coercive force. Therefore, even if the ferrite sintered magnet and the bond magnet are thinly processed for mounting on a small motor and generator, the efficiency of the motor or generator can be maintained at a sufficiently high level. ..

Ferrite sintered magnets and bond magnets are used, for example, for fuel pumps, power windows, ABS (anti-lock braking system), fans, wipers, power steering, active suspensions, starters, and door locks. , Can be used as a magnet for automobile motors such as for electric mirrors. Also, for FDD spindles, VTR capstans, VTR rotating heads, VTR reels, VTR loadings, VTR camera capstans, VTR camera rotating heads, VTR camera zooms, VTR camera focus, radio cassettes, etc. Ferrite sintered magnets and bonded magnets can be used as magnets for OA / AV equipment motors for CD / DVD / MD spindles, CD / DVD / MD loading, CD / DVD optical pickups, and the like. Further, ferrite sintered magnets and bond magnets can also be used as magnets for motors for home appliances such as air conditioner compressors, freezer compressors, electric tool drives, dryer fans, shaver drives, and electric toothbrushes. .. Furthermore, ferrite sintered magnets and bond magnets can also be used as magnets for FA equipment motors such as robot shafts, joint drives, robot main drives, machine equipment table drives, and machine equipment belt drives. ..

The contents of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

(Example 1)
[Manufacturing of ferrite sintered magnets]
<Mixing process and addition process>
Lanthanum hydroxide (La (OH) ₃ ), cobalt oxide (Co ₃ O ₄ ), iron oxide (Fe ₂ O ₃ ), and calcium carbonate (CaCO ₃ ) were prepared as raw materials for the ferrite phase. These raw materials, boric acid (H ₃ BO ₃ ), silicon dioxide (SiO ₂ ), and water were mixed and pulverized for 10 minutes using a wet attritor to prepare a slurry of the raw material mixture. As described below, the proportion of each raw material in the raw material mixture was adjusted to match the composition of the metal component of the ferrite phase (component represented by the following general formula (Ib)) shown in Table 1 below.
La _{1-x Ca x} F my _Coy (Ib)

The ratio of the lanthanum compound in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of La ₂ O ₃ .
The ratio of the calcium compound in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of the mass of CaO.
The ratio of the iron compound in the raw material mixture was the value (unit: mass%) shown in Table 1 below in terms of mass of Fe ₂ O ₃ .
The ratio of the cobalt compound in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below in terms of mass of Co ₃ O ₄ .
The ratio of boric acid (addition amount of H ₃ BO ₃ ) in the raw material mixture was adjusted to the value (unit: mass%) shown in Table 1 below.
The ratio of silicon dioxide (addition amount of SiO ₂ ) in the raw material mixture was adjusted to 0.19% by mass.

<Take-baking process (heating process)>
After drying the slurry of the raw material mixture, the raw material mixture was held at 1280 ° C. for 2 hours in the air to obtain calcined powder (coarse ferrite particles).

<Crushing process>
In the coarse pulverization step, the calcination powder was pulverized with a vibration mill for 9 minutes to adjust the BET specific surface area of the calcination powder to the range of 0.5 to 1.5 m ² / g. In the fine pulverization step following the coarse pulverization step, the calcined powder was further pulverized with a wet ball mill for 36 hours to obtain a slurry containing ferrite particles (slurry of an intermediate material). The BET specific surface area of the ferrite particles in the slurry was in the range of 7 to 10 m ² / g.

<Molding process>
The slurry of the intermediate material was dehydrated by a centrifuge to adjust the concentration of the solid content in the slurry within the range of 73 to 76% to obtain a slurry for wet molding. This slurry was molded in an applied magnetic field of 10 kOe to obtain a cylindrical molded body. A wet magnetic field molding machine was used for molding.

<Baking process>
The molded product was sufficiently dried in the air at room temperature. The dried molded body was held in the air at 1175 ° C. for 1 hour to obtain a sintered body (ferrite sintered magnet of Example 1).

[Analysis of composition]
The composition of the ferrite sintered magnet was analyzed by XRF method and ICP emission spectroscopy. The composition of the metal component contained in the ferrite sintered magnet of Example 1 is represented by the above general formula (1b), and the values of 1-x, x, my and y in the general formula (1b) are , It was confirmed that the values are shown in Table 1 below. It was confirmed that the content of boron in the ferrite sintered magnet is the value shown in Table 1 below in terms of the mass of boric acid (H ₃ BO ₃ ). It was confirmed that the content of boron in the ferrite sintered magnet is the value shown in Table 1 below in terms of the mass of elemental boron (B). It was confirmed that the content of boron in the ferrite sintered magnet is the value shown in Table 1 below in terms of mass of boron oxide ( _{B2O 3 )} .

[Measurement of magnetic characteristics]
After processing the upper surface and the lower surface of the cylindrical ferrite sintered magnet, the residual magnetic flux density Br (mT) and the coercive force HcJ (kA / m) of the ferrite sintered magnet were measured. A BH tracer having a maximum applied magnetic field of 25 kOe was used for the measurement. Br, HcJ and square ratio (Hk / HcJ) of Example 1 are shown in Table 1 below.

(Examples 2 to 9)
The ratio of boric acid (addition amount of H ₃ BO ₃ ) in each of the raw material mixtures of Examples 2 to 9 was adjusted to the value (unit: mass%) shown in Table 1 below. Ferrite sintered magnets of Examples 2 to 9 were produced in the same manner as in Example 1 except for the proportion of boric acid in the raw material mixture. The composition of each of the ferrite sintered magnets of Examples 2 to 9 was analyzed by the same method as in Example 1. The results of the analysis are shown in Table 1 below. The magnetic properties of the ferrite sintered magnets of Examples 2 to 9 were measured by the same method as in Example 1. The measurement results are shown in Table 1 below.

(Examples 10 to 17)
In Examples 10 to 17, the ratio of each raw material (La compound, Ca compound, Fe compound, Cо compound) and boric acid in the raw material mixture is adjusted to each value (unit: mass%) shown in Table 1 below. rice field. Ferrite sintered magnets of Examples 10 to 17 were produced in the same manner as in Example 1 except for the composition of the raw material mixture. The composition of each of the ferrite sintered magnets of Examples 10 to 17 was analyzed by the same method as in Example 1. The results of the analysis are shown in Table 1 below. The magnetic properties of the ferrite sintered magnets of Examples 10 to 17 were measured by the same method as in Example 1. The measurement results are shown in Table 1 below. In any of Examples 1 to 17, a sufficiently high HcJ of 500 kA / m or more could be obtained.

(Comparative Examples 1 to 3)
In the preparation of the raw material mixture of Comparative Examples 1 to 3, boron oxide (B ₂ O ₃ ) was used as the boron source instead of boric acid. The ratio (addition amount) of boron oxide in each of the raw material mixtures of Comparative Examples 1 to 3 was adjusted to the value (unit: mass%) shown in Table 1 below. Ferrite sintered magnets of Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except for the composition of the boron source and the amount added. The composition of each of the ferrite sintered magnets of Comparative Examples 1 to 3 was analyzed by the same method as in Example 1. The results of the analysis are shown in Table 1 below. The magnetic properties of the ferrite sintered magnets of Comparative Examples 1 to 3 were measured by the same method as in Example 1. The measurement results are shown in Table 1 below.

According to the present invention, ferrite particles, ferrite sintered magnets and bonded magnets having a sufficiently high coercive force are provided. Ferrite sintered magnets having a high coercive force or the above-mentioned bonded magnets are applied to, for example, permanent magnets for motors.

Claims (9)

A method for manufacturing a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure.
A calcining step of producing ferrite particles by calcining a mixture containing the raw material of the ferrite phase, and a calcining step.
A molding step of molding an intermediate material containing the ferrite particles to prepare a molded body, and
An addition step of adding boric acid to at least one of the mixture before calcination and the intermediate material before molding.
The firing process for sintering the molded product and
Equipped with
The ratio of the boric acid to the total mass of the mixture containing the boric acid or the total mass of the intermediate material containing the boric acid is more than 0.3% by mass and 2.5% by mass or less .
The raw materials for the ferrite phase are a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron, and a compound of cobalt.
R is at least one element selected from rare earth elements,
A is a combination of at least one alkaline earth metal element other than calcium and calcium, or only calcium.
The ratio of the compound of the rare earth element R to the mass of the whole mixture containing the boric acid or the mass of the intermediate material containing the boric acid is 5.5% by mass or more in terms of the mass of the oxide of R 19. .9% by mass or less,
The ratio of the compound of the alkaline earth metal element A to the mass of the whole mixture containing the boric acid or the mass of the intermediate material containing the boric acid is 1.7 mass in terms of the mass of the oxide of A. % Or more and 7.6% by mass or less,
The ratio of the iron compound to the total mass of the mixture containing the boric acid or the total mass of the intermediate material containing the boric acid is 45.3% by mass or more and 87.4 in terms of the mass of the iron oxide. Is less than% by mass and
The ratio of the cobalt compound to the total mass of the mixture containing the boric acid or the total mass of the intermediate material containing the boric acid is 0.9% by mass or more in terms of the mass of the cobalt oxide, 18.9. It is less than% by mass and
The metal component contained in the ferrite phase is represented by R _{1-x A} x F _{my Coy} .
x satisfies 0.2 ≦ x ≦ 0.8,
y satisfies 0.1 ≦ y ≦ 0.65,
m satisfies 3 ≦ m <14,
The content of boron in the ferrite sintered magnet is 0.1% by mass or _more and 0.6% by mass or less in terms of mass of _B2O3 .
In the addition step, the boric acid and silicon dioxide are added to the mixture or the intermediate material.
The ratio of the silicon dioxide to the total mass of the mixture containing the boric acid and the silicon dioxide is more than 0% by mass and 0.19% by mass or less.
Or,
The ratio of the silicon dioxide to the total mass of the intermediate material containing the boric acid and the silicon dioxide is more than 0% by mass and 0.19% by mass or less.
Manufacturing method of ferrite sintered magnet. The ratio of the boric acid to the mass of the whole mixture or the whole intermediate material is 0.6% by mass or more and 1.5% by mass or less.
The method for manufacturing a ferrite sintered magnet according to claim 1 . The ratio of the boric acid to the mass of the whole mixture or the whole intermediate material is 0.7% by mass or more and 1.2% by mass or less.
The method for manufacturing a ferrite sintered magnet according to claim 1 or 2 . At least one of the mixture before calcination and the intermediate material before molding contains water.
The method for manufacturing a ferrite sintered magnet according to any one of claims 1 to 3 . A method for producing ferrite particles containing a ferrite phase having a magnetoplumbite-type crystal structure.
A heating step for producing ferrite particles by heating a mixture containing the raw material of the ferrite phase and boric acid is provided.
The ratio of the boric acid to the total mass of the mixture containing the boric acid is more than 0.3% by mass and 2.5% by mass or less .
The raw materials for the ferrite phase are a compound of rare earth element R, a compound of alkaline earth metal element A, a compound of iron, and a compound of cobalt.
R is at least one element selected from rare earth elements,
A is a combination of at least one alkaline earth metal element other than calcium and calcium, or only calcium.
The ratio of the compound of the rare earth element R to the total mass of the mixture containing boric acid is 5.5% by mass or more and 19.9% by mass or less in terms of the mass of the oxide of R.
The ratio of the compound of the alkaline earth metal element A to the total mass of the mixture containing boric acid is 1.7% by mass or more and 7.6% by mass or less in terms of the mass of the oxide of A.
The ratio of the iron compound to the total mass of the mixture containing boric acid is 45.3% by mass or more and 87.4% by mass or less in terms of the mass of iron oxide.
The ratio of the cobalt compound to the total mass of the mixture containing boric acid is 0.9% by mass or more and 18.9% by mass or less in terms of the mass of the cobalt oxide.
The metal component contained in the ferrite phase is represented by R _{1-x A} x F _{my Coy} .
x satisfies 0.2 ≦ x ≦ 0.8,
y satisfies 0.1 ≦ y ≦ 0.65,
m satisfies 3 ≦ m <14,
The content of boron in the ferrite particles is 0.1% by mass or _more and 0.6% by mass or less in terms of mass of _B2O3 .
The boric acid and silicon dioxide are added to the mixture and
The ratio of the silicon dioxide to the total mass of the mixture containing the boric acid and the silicon dioxide is more than 0% by mass and 0.19% by mass or less.
Method for manufacturing ferrite particles. The ratio of the boric acid to the total mass of the mixture is 0.6% by mass or more and 1.5% by mass or less.
The method for producing ferrite particles according to claim 5 . The ratio of the boric acid to the total mass of the mixture is 0.7% by mass or more and 1.2% by mass or less.
The method for producing ferrite particles according to claim 5 or 6 . The mixture before being heated contains water,
The method for producing ferrite particles according to any one of claims 5 to 7 . The process of manufacturing ferrite particles and
A step of producing a molded product containing the ferrite particles and a resin, and
The step of curing the resin in the molded body and
Equipped with
The ferrite particles are produced by the production method according to any one of claims 5 to 8 .
How to manufacture a bond magnet.